-(1) Baby Crying for deaf parent : shortcuts
I have a few potential solutions in mind:
Well… my cheeks are red, now. Though all is not totally lost to my idiocy/privilege:
A low-frequency tone should produce tactile vibrations - one of the variables users cannot vary about device vibrations. I think iPhone’s speakers are rated down to 40 Hz, if memory serves.
Here’s a sample audio file that includes 40Hz, 60Hz, 80Hz, and 100Hz 10 second segments.